1. Field of the Invention
The present invention relates generally to an apparatus and a method for sealably setting a tubular liner inside a cylindrical well casing, and more particularly to an improved two piece liner setting apparatus and method for installing a liner with an improved degree of precision in the seal between the liner setting apparatus and the well casing.
When removing oil from oil wells and the like, it is desirable to inhibit the amount of particulates such as sand which are allowed into the line. This is generally accomplished by using a finely perforated tubular disposed within the well casing of the well closely adjacent to the bottom thereof. The perforated tubular liner thus acts as a strainer to inhibit the passage of sand and like particulates into the line through which the production fluid is drawn from the well.
Such perforated tubular liners generally have an outer diameter which is substantially smaller than the inner diameter of the well casing, thus creating an annular passage between the well casing and the liner. This annular passage allows the production fluid to be drawn radially into the perforated tubular liner, and then upwardly from the well through an elongated string of production tubing lowered into the well casing into fluid communication with the liner. The lower end of the production tubing is generally inserted into the top of the liner, and will operate to draw essentially particulate-free production fluid from the well by suction.
In order to ensure that all production fluid removed from the well passes through the perforated tubular liner, it is necessary to provide a secure seal between the top of the liner and the interior of the well casing. This seal will prevent the passage of particulate matter upward between the well casing and the liner, and then downward into the open end of the liner and into the production fluid drawn from the well. Typically, a seal ring with a diameter approximately equal to the inner diameter of the well casing is disposed at the top of the liner, with the liner being installed by forcing the seal ring into the well casing and sliding the liner down to the bottom of the well casing.
During the installation of the liner, the seal ring is frequently damaged, particularly when the inner wall of the casing is roughened by cement deposits or scale, or when the segments of the casing are misaligned, kinked, out of round, or otherwise damaged. In addition to rendering the seal ineffective, this damage frequently makes installation of the production tubing difficult or impossible. These disadvantages and problems in the art were largely solved by the introduction of the liner setting apparatus described in U. S. Pat. No. 3,568,773, to Chancellor et al., which patent is commonly owned together with the present invention, and which patent is hereby incorporated herein by reference.
The Chancellor et al. device uses a flaring plate to expand a sealing flange on the top of a setting sleeve attached to the top of the liner. Following installation of the liner at the bottom of the well casing, the tubing string is reciprocated to impact on the top of the flaring plate, thereby expanding the sealing flange into a tight sealing relationship with the interior of the well casing. This system works remarkably well, and has only two disadvantages. First, when installing the liner, the flaring plate has a tendency to expand the sealing flange prematurely, particularly when the setting sleeve becomes momentarily stuck in the casing while the liner is being lowered into the well. This problem seriously inhibits the ability to install the liner, particularly in well casings which are more damaged than is typical.
The second problem is a movement off center by the setting sleeve caused by the flaring plate not seating properly. This may result in a non-uniform seal, a substandard seal, or even the lack of a seal in isolated instances. Despite these problems, the Chancellor et al. device represented a great improvement in the ability to properly install liners. It will be appreciated, however, that it is desirable to overcome the problems associated with this device.
Accordingly, it is an objective of the present invention to provide for an improved liner setting apparatus and method which will be easier to install, and which will not expand the seal prematurely. As such, it is desirable to completely and positively inhibit the expansion of the seal until the liner is in place at the bottom of the casing, and this is also an objective of the present invention. It is also an objective of the present invention to ensure proper alignment of the liner setting apparatus, to prevent the apparatus from moving off center. The present invention also has as an objective the consistent formation of a uniform seal. Finally, these objectives and advantages must all be achieved without incurring any relative disadvantage.